Nitrous Oxide Emission from Grazed Grassland Under Different Management Systems

• Published in: Ecosystems (New York) 2011-06, Vol.14 (4), p.563-582
• Main Authors: Rafique, Rashad, Hennessy, Deirdre, Kiely, Gerard
• Format: Article
• Language: English
• Subjects: Agricultural soils; Agrology; Air quality management; Animal and plant ecology; Animal, plant and microbial ecology; Anthropogenic factors; Biological and medical sciences; Biomedical and Life Sciences; Climate change; Climatic changes; Ecology; Ecosystems; Emission measurements; Emissions; Environmental Management; Environmental protection; EPA; Fluctuations; Fundamental and applied biological sciences. Psychology; General aspects; Geoecology/Natural Processes; Global temperature changes; Grasses; Grassland soils; Grasslands; Grazing; Grazing management; Hydrology/Water Resources; Intergovernmental Panel on Climate Change; Life Sciences; Nitrous oxide; Pastures; Plant Sciences; Pollutant emissions; Pores; Soil; Soil water; Synecology; Zoology
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-011-9434-x

Nitrous oxide (N₂O) emissions from grazed grasslands are estimated to be approximately 28% of global anthropogenic N₂O emissions. Estimating the N₂O flux from grassland soils is difficult because of its episodic nature. This study aimed to quantify the N₂O emissions, the annual N₂O flux and the emission factor (EF), and also to investigate the influence of environmental and soil variables controlling N₂O emissions from grazed grassland. Nitrous oxide emissions were measured using static chambers at eight different grasslands in the South of Ireland from September 2007 to August 2009. The instantaneous N₂O flux values ranged from -186 to 885.6 μg N₂O-N m⁻² h⁻¹ and the annual sum ranged from 2 ± 3.51 to 12.55 ± 2.83 kg N₂O-N ha⁻¹ y⁻¹ for managed sites. The emission factor ranged from 1.3 to 3.4%. The overall EF of 1.81% is about 69% higher than the Intergovernmental Panel on Climate Change (IPCC) default EF value of 1.25% which is currently used by the Irish Environmental Protection Agency (EPA) to estimate N₂O emission in Ireland. At an N applied of approximately 300 kg ha⁻¹ y⁻¹, the N₂O emissions are approximately 5.0 kg N₂O-N ha⁻¹ y⁻¹, whereas the N₂O emissions double to approximately 10 kg N ha⁻¹ for an N applied of 400 kg N ha⁻¹ y⁻¹. The sites with higher fluxes were associated with intensive N-input and frequent cattle grazing. The N₂O flux at 17°C was five times greater than that at 5°C. Similarly, the N₂O emissions increased with increasing water filled pore space (WFPS) with maximum N₂O emissions occurring at 60-80% WFPS. We conclude that N application below 300 kg ha⁻¹ y⁻¹ and restricted grazing on seasonally wet soils will reduce N₂O emissions.